Two correct answers are in circulation at once because the standard moved by drift rather than by decision. Emily Post's 1922 edition set the rule at 10% of the bill for a meal in a first-class hotel, with a 25-cent minimum. By the second half of the century the accepted figure was 15%, and Post's 1997 edition recorded the next move in progress: it wasn't long ago, it said, that 15 percent was considered a generous tip in elegant restaurants, and now the figure is moving toward 20 percent for excellent service. Nobody announced the change, so people learned whichever number was current when they started paying restaurant bills, and both cohorts are still alive and still eating out. That is what the polling shows. Asked what they leave for average service, 27% of Americans say 15% and 35% say 20%. Those are the two largest answers, adjacent and nearly equal. Asked by Pew about an explicitly average meal, 57% say they would tip 15% or less while a quarter say 20% or more. Neither group thinks it is being stingy or extravagant; each is applying the rule it was taught.